1. Field of the Invention
The present invention relates to a solar cell structural body comprising a solar cell and a concrete member, particularly a solar cell structural body comprising a solar cell arranged on a concrete retaining body such that part of a conductor portion of said solar cell is contacted with said concrete retaining body a solar cell array and a sunlight power generation system in which said solar cell structural body is used. The term xe2x80x9cconductor portionxe2x80x9d in the present invention means an exposed conductor portion extending from the electrode of the solar cell.
2. Related Background Art
In recent years, societal consciousness of the problems relating to the environment and energy has been increasing all over the world. Particularly, the earth warming because of the so-called greenhouse effect due to an increase of atmospheric CO2 has been predicted to cause a serious problem. In view of this, public attention has been focused on a sunlight power generation system (that is, a solar cell power generation system) for the reason that it is a clean power generation system which generates electric power using sunlight, which is evenly accessible at any place In the world, as the power generation energy source, and which can attain relatively high power generation efficiency without necessity of using a complicated large installation.
Presently, as such sunlight power generation system, a variety of solar cell modules have been used at certain private residential buildings and at certain public facilities and also for portable appliances. However, such solar cell modules are still expensive. This situation has presented a major obstacle in making the use of solar cell modules more widespread not only at private residential buildings but also at public facilities.
As one of the measures to overcome this obstacle, there can be mentioned a manner of integrating a solar cell module with a relatively inexpensive product in a different industrial field to diminish the total cost. As a typical example of a solar cell module of the type installed on a building structural body, there can be mentioned a trestle installation type solar cell module comprising a framed solar cell module installed on a trestle provided on a roof and a building material integral type solar cell module comprising a solar cell module integrated with a building material. These solar cell modules presently have been spotlighted for the reasons that the material cost can be diminished because a roofing material as a separate member is not required to be used and the construction cost upon the installation can be diminished because they can be installed in the same manner as in the ordinary roof installation, where the solar cell modules can be installed on a roof of a building at a relatively low cost in terms of the total cost. In addition, the roof installed with any of these solar cell modules has a beautiful exterior appearance which is in harmony with surrounding roofs.
Solar cell modules in recent years which are represented by aforementioned solar cell modules are of value-added types integrated with products in various industrial fields. To be more specific, these solar cell modules share the material costs and the production costs of the two members, and when the shared costs are considered as the total cost, it can be said that the total cost is markedly reduced.
Separately, for the sunlight power generation system, it is expected to be used at power generation facilities in the near future as a new energy source to replace the present energy source.
Incidentally, in order to comply with the consumption of power which has been continuously increasing year by year, power generation facilities have been newly established in recent years. Particularly, the consumption of power becomes significant during day time, when people work in the offices and the like, where it often reaches a peak mainly due to a significant increase in the energy consumed in operating the equipment used for office work and the like. In addition, especially during summer time, the consumption of power frequently reaches a peak due to a marked increase in the energy consumed in operating cooling systems. This phenomenon of reaching a peak in terms of the consumption of power is generally called an energy peak.
Now, the power generation facilities newly established up to the present time include thermal power stations, hydraulic power stations, atomic power stations and the like. However, in recent years, in the light of prevention of the earth warming, environmental protection and the like, sunlight power generation, wind power generation, geothermal power generation and the like have been spotlighted.
The peak energy time zone in summer time or day time is a time zone when sunlight is irradiated. Thus, public attention is focused on a sunlight power generation plant where a sunlight power generation system having a performance capable of generating a large energy (power) in the peak energy time zone is used as the power source.
However, in the case where a solar cell module is used as the sunlight power generation system as the power source in the sunlight power generation plant, the power generation cost (the cost of the power generated) becomes very high as long as an ordinary solar cell module is used as said solar cell module. In order to improve this situation, it is considered to be effective to adopt the foregoing manner in that a solar cell module is integrated with a relatively inexpensive product in a different industrial field so as to share the material costs and the production costs of the two members, whereby the total cost is reduced.
However, when such a solar cell module is used as the power source in a sunlight power generation plant, the essential function is to generate power and other functions are not necessitated necessary. To be more specific, for use together with the power source in a thermal power station or the like, it is a very important factor to use not such value-added solar cell module but a relevant solar cell module which is the same as the power source in the thermal power station or the like in terms of the power generation cost. In light of prevention of global warming, environmental protection and the like, it is ideal to use only a relevant sunlight power generation system which provides clean energy. However, since the sunlight power generation system is excessively costly, it is almost impossible that the new power source replaces the conventional power source.
To be more specific, any of the presently available solar cell modules which are costly in terms of the cost of the power generated is very difficult to use as the power source in the power plant.
The foregoing power generation cost is obtained from the equation: power generation cost=[(annual apparatus cost) +(annual repair cost+annual maintenance cost)+(annual fuel cost)]/(annual generated power quantity). The annual apparatus cost here means a cost obtained by dividing the total construction expense (the total initial investment amount) by the service life year of the power generation system. However, in this case, the interests must be taken into consideration. The xe2x80x9cannual repair cost+annual maintenance costxe2x80x9d means the sum of the annual expenses required for the maintenance of the power generation system. The annual fuel cost means the sum of the annual expenses required for the fuel necessary to operate the power generation system.
In the case of a sunlight power generation system in which a solar cell module is used, unlimited solar energy which is evenly accessible at any place in the world is used in order to generate electric power and therefore, the above-mentioned annual fuel cost is not necessitated. In addition, the xe2x80x9cannual repair cost+annual maintenance costxe2x80x9d does not become considerable. A main factor to increase the power generation cost in the case of the sunlight power generation system is the annual apparatus cost, where the watt cost of the solar cell module is considerable.
Under such circumstance, in order to make the use of the sunlight generation system to be more widely spread and in order to make the sunlight generation system capable of being used as the power source in the power generation station, it is essential to greatly reduce the power generation cost. To be more specific, it is essential that the watt cost of the solar cell module and the apparatus cost are reduced so that the power generation cost is competitive with that in any of the current power generation systems.
In the following, description will be made of the foregoing cost relating to the solar cell module.
In the case of a sunlight power generation system in which a solar cell module, the system is designed on the assumption that ordinary people who are not acquainted with electric things including solar cells will use and touch the system. For doing in this way, a number of materials are necessary to be used in order to enhance the security and because of this, the material cost is unavoidably increased. In addition, thermocompression process is required to perform in the production of the solar cell module, where the man-hour becomes considerable and the productivity is reduced. Thus, the production cost of the solar cell module is eventually raised. That is, the power generation cost as a whole is raised. As long as the solar cell module is produced in this way, there is a limit for reducing the watt cost of the solar cell module.
In the case of a solar cell module used in the power generation station, the solar cell module is used under controlled environment. The controlled environment here means a location where only specialists (handling persons) who are acquainted with electric things including solar cells are admitted to enter therein but any other persons are prohibited from entering therein. In order to establish such controlled atmosphere, it takes a measure such that a fence or a wall is provided around an external enclosure for the solar cell module or/and a key is provided at the entrance of the location where the solar cell module is present. And the controlled atmosphere is made so that the handling persons can perform periodical maintenance works for the solar cell module. Because the solar cell module is used under such controlled environment, the specification relating to the safety and insulation of the solar cell module can be mitigated.
For the installation method of the solar cell module, there are known a method wherein a frame body is provided at a solar cell module and the frame body is installed on a trestle and a method wherein a steel plate is provided at the back face side of a solar cell module and the steel plate is processed, followed by being installed on a trestle. However these methods have disadvantages such that a number of materials are required to be used, along with this the number of operations is increased, and as a result, the installation cost is raised.
In order to diminish the installation cost, there are various proposals of a method wherein a solar cell module is provided at a relatively inexpensive concrete member capable of being used as a back face member or a trestle for the solar cell module.
Particularly, Japanese Laid-open Patent Publication No. 11(1999)-270023 (hereinafter referred to as document 1) discloses a wall panel (a panel for a wall) which comprises a panel main body comprising a light weight foamed concrete member provided with a recessed portion having a prescribed depth at the surface thereon and a solar cell module embedded in said recessed portion. Document 1 describes that because the solar cell module is installed in the recessed portion of the concrete member so as to integrate with the panel main body, not only the execution work efficiency but also the maintenance work efficiency are improved.
Japanese Laid-open Patent Publication No. 2001-60704 (hereinafter referred to as document 2) discloses a photoelectric conversion apparatus comprising a first electrode layer, a semiconductor layer and a second electrode layer sequentially stacked in this order on a substrate, and a sealing resin film disposed to cover the surface of the second electrode layer, wherein a temporary peeling film is clad on the sealing resin film through an adhesive layer such that the temporary peeling film is capable of being peeled, and wherein the adhesive layer, after the temporary peeling film is peeled, provides a sticky face for a member on which the photoelectric conversion apparatus is mounted. In document 2, there are illustrated a concrete plate, a slate plate, a roof tile, a metal plate, and the like. Document 2 describes that because of using the temporary peeling film, not only the execution work efficiency but also the maintenance work efficiency are improved.
Japanese Laid-open Utility Model Publication No. 5(1993)-3430 (hereinafter referred to as document 3) discloses a power generation roof tile comprising a roof tile main body made of a cement or a metal and a solar cell bonded on the surface of a functioning portion of the roof tile main body, wherein an opaque sheet which is difficult to slip is bonded on the surface of the solar cell in a state capable of being peeled. Document 3 describes that when the power generation roof tile is installed, power generation by the solar cell does not takes place because the solar cell is covered by the opaque sheet and therefore, the execution work can be securely performed while preventing the surface of the solar call from being damaged or stained.
In the case of a power generation station or the like it which a sunlight power generation system is used as the power source, all the accommodations are necessary to be installed within a controlled environment, where any person besides the persons concerned who are acquainted with electric things is not allowed to enter therein.
The present inventors conceived a solar cell structural body having a solar cell whose conductor portions are partly contacted with a concrete retaining body provided to retain said solar cell from the non-light receiving face side, which would be suitable to install in such controlled environment as described in the above.
FIGS. 12(A) and 12(B) are schematic views for explaining a solar cell whose exposed conductor portions are partly contacted with a concrete retaining body (not shown) provided to retain the solar cell from the non-light receiving face side. Particularly, FIG. 12(A) is a schematic view illustrating a solar cell [which is retained on a concrete retaining body (not shown)] before a weathering-resistant coat film is formed thereon. FIG. 12(B) is a schematic view illustrating said solar cell after said weathering-resistant coat film is formed thereon.
In FIGS. 12(A) and 12(B), reference numeral 1201 indicates a photovoltaic element, reference numeral 1202 a positive electrode, reference numeral 1203 a negative electrode, and reference numeral 1204 a weathering-resistant coat film. The solar cell means a structure comprising a photovoltaic element 1201, a positive electrode 1202 and a negative electrode 1203.
By forming a weathering-resistant coat film 1204 on the light-receiving face side of the solar cell as shown in FIG. 12(B), it is possible to make the solar cell [see, FIG. 12(A)] have weathering-resistance.
To be more specific, the photovoltaic element 1201 is made so as to have weathering-resistance by forming the weathering-resistant coat film 1204 so as to cover the light-receiving face thereof, wherein for the positive electrode 1202 and the negative electrode 1203, at least their portions which serve to electrically connect the solar cell with an adjacent solar cell (not shown) are exposed without being covered by the coat film, where there will be an occasion in that the exposed portions (that is, the exposed conductor portions) of the positive and negative electrodes of the solar cell are directly contacted with the concrete retaining body (not shown). And if the structure should be such that a clearance is present between the solar cell and the concrete retaining body, there will be an occasion in that aforesaid exposed conductor portions of the positive and negative electrodes of the solar cell are indirectly contacted with the concrete retaining body through rain water or the like present in said clearance.
Now, the present inventors conducted trials in the following manner.
Focusing on a relatively inexpensive concrete member as a trestle, a plate member made of a concrete was arranged on the ground and the base member of the foregoing solar cell is directly mounted on the concrete plate member to form a solar cell installed structural body (hereinafter referred to as xe2x80x9csolar cell structural bodyxe2x80x9d). In this way, a plurality of solar cell structural bodies were formed. And these solar cell structural bodies were connected with each other in series connection to form a solar cell array.
The solar cell array thus formed was subjected to power generation. As a result, it was found that such shortcomings as will be described below and which are required to be solved are present.
That is, in the case of a solar cell structural body in which a concrete member is used as the retaining body, as the concrete member, there is used a concrete member which is generally formed from a mixture composed of a cement, water, an aggregate (comprising fine aggregates and rough aggregates) and the like. Thus, the electric resistance value of the concrete member greatly differs depending on the mixing ratio of these materials. In addition, because the concrete member has water absorption properties, the specific resistance value (the resistivity) thereof is reduced when the concrete member absorbs water. Therefore, depending on the installation form of the solar cell structural body, a problem may arise that leakage current from the exposed conductor portions of the solar cell which are contacted with the concrete member flows to the installation face while passing through the concrete member, where a large power loss occurs.
Accordingly, the present invention is aimed at solving the foregoing problem that occurs because the exposed conductor portions of the solar cell are contacted with the concrete member as described in the above.
Another object of the present invention is to provide a solar cell structural body which is always free from the aforesaid problem without depending on the installation form.
A further object of the present invention is to provide a solar cell array in which said solar cell structural body is used.
A still further object of the present invention is to provide a sunlight power generation system in which said solar cell structural body is used.
A typical embodiment of the solar cell structural body of the present invention has a solar cell arranged on a concrete retaining body comprising a concrete prepared from a mixture comprising at least a cement, water and an aggregate, such that part of a conductor portion of said solar cell is contacted with said concrete retaining body, characterized in that said concrete member has a resistivity in a range of from 9xc3x97103 to 120xc3x97103 xcexa9xc2x7cm.
The solar cell structural body of the present invention is preferred to additionally include the following features:
that the water to cement ratio of the concrete upon the production thereof is less than 40% by weight;
that the mixing ratio of the aggregate to the cement is at least 1:4 by weight;
that the cement comprises a Portland cement or an alumina cement;
that the concrete comprises a concrete hardened in atmospheric air;
that the concrete retaining body serves as a back face member or a trestle for the solar cell;
that the retaining body does not contain a reinforcement;
that the solar cell has two electrically conductive portions having a different polarity, one on the light receiving face side and the other on the non-light receiving face side; and
that when the density of the concrete retaining body is made to be d[Kg/m3], the inclination angle of the retaining body from the ground face is made to be xcex8, and the thickness of the retaining body is made to be t[m], the relation equation: t greater than 1307.9 (0.71+0.016xc3x97xcex8)/(dxc3x97gxc3x97cos xcex8) is established.
The solar cell array of the present invention is characterized in that said solar cell array has a plurality of solar cell structural bodies having such configuration as above described which are connected with each other in series connection.
In a preferred embodiment, a positive electrode terminal or a negative electrode terminal of the solar cell array is electrically grounded.
The sunlight power generation system of the present invention is characterized in that said sunlight power generation system has a connection body in which one or more solar cell structural bodies having such configuration as above described are electrically connected and said connection body has a positive electrode terminal and a negative electrode terminal which are connected to an inverter having a ground sensor accommodated therein.
In a preferred embodiment, each solar cell structural body has a ground current Ileak of less than 100 mA.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings.